Comments

This patch adds a function named ext4_update_super() which updates
super block and whose code is copied from ext4_group_add().
The function will be used by new resize implementation.
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
---
fs/ext4/resize.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 72 insertions(+), 0 deletions(-)

Patch

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.cindex 66ca671..d20b29c 100644--- a/fs/ext4/resize.c+++ b/fs/ext4/resize.c@@ -831,6 +831,78 @@ static int ext4_setup_new_desc(handle_t *handle, struct super_block *sb,
return err;
}
+/*+ * ext4_update_super() updates super so that new the added group can be seen+ * by the filesystem.+ *+ * @sb: super block+ */+static void ext4_update_super(struct super_block *sb,+ struct ext4_new_group_data *input)+{+ struct ext4_sb_info *sbi = EXT4_SB(sb);+ struct ext4_super_block *es = sbi->s_es;++ /*+ * Make the new blocks and inodes valid next. We do this before+ * increasing the group count so that once the group is enabled,+ * all of its blocks and inodes are already valid.+ *+ * We always allocate group-by-group, then block-by-block or+ * inode-by-inode within a group, so enabling these+ * blocks/inodes before the group is live won't actually let us+ * allocate the new space yet.+ */+ ext4_blocks_count_set(es, ext4_blocks_count(es) ++ input->blocks_count);+ le32_add_cpu(&es->s_inodes_count, EXT4_INODES_PER_GROUP(sb));++ /*+ * We need to protect s_groups_count against other CPUs seeing+ * inconsistent state in the superblock.+ *+ * The precise rules we use are:+ *+ * * Writers must perform a smp_wmb() after updating all dependent+ * data and before modifying the groups count+ *+ * * Readers must perform an smp_rmb() after reading the groups count+ * and before reading any dependent data.+ *+ * NB. These rules can be relaxed when checking the group count+ * while freeing data, as we can only allocate from a block+ * group after serialising against the group count, and we can+ * only then free after serialising in turn against that+ * allocation.+ */+ smp_wmb();++ /* Update the global fs size fields */+ sbi->s_groups_count++;++ /* Update the reserved block counts only once the new group is+ * active. */+ ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) ++ input->reserved_blocks);++ /* Update the free space counts */+ percpu_counter_add(&sbi->s_freeblocks_counter,+ input->free_blocks_count);+ percpu_counter_add(&sbi->s_freeinodes_counter,+ EXT4_INODES_PER_GROUP(sb));++ if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&+ sbi->s_log_groups_per_flex) {+ ext4_group_t flex_group;+ flex_group = ext4_flex_group(sbi, input->group);+ atomic_add(input->free_blocks_count,+ &sbi->s_flex_groups[flex_group].free_blocks);+ atomic_add(EXT4_INODES_PER_GROUP(sb),+ &sbi->s_flex_groups[flex_group].free_inodes);+ }++}+
/* Add group descriptor data to an existing or new group descriptor block.
* Ensure we handle all possible error conditions _before_ we start modifying
* the filesystem, because we cannot abort the transaction and not have it